1. Technical Field
The present invention relates to a circuit device and an electronic apparatus.
2. Related Art
A method of controlling driving of a motor by controlling a chopping current is known as a motor driver that drives a DC motor. With this method, current flowing in an H bridge circuit is subjected to current-to-voltage conversion using a sense resistor, the obtained voltage is compared with a reference voltage, and thereby the chopping current is detected. Then, a motor is caused to rotate at a constant speed by feeding the detection result back to the control circuit and subjecting the driving signal of the bridge circuit to PWM control. The techniques disclosed in JP-A-2008-42975 and JP-A-2010-12873 are known as examples of this kind of prior technique for a motor driver.
The bridge circuit of the motor driver has first to fourth transistors (switch elements) for driving, and the first and fourth transistors are electrically connected to the opposite ends of the motor and the second and third transistors are similarly connected to the motor. Also, in a charge period, the first and fourth transistors are on. This sets the positive terminal (+terminal) of the motor to a voltage with a high potential and sets the negative terminal (−terminal) to a voltage with a low potential. On the other hand, in a decay period, the second and third transistors are on. This sets the positive terminal of the motor to a voltage with a low potential and sets the negative terminal to a voltage with a high potential.
However, with prior motor drivers, a sense resistor for current detection is provided between the bridge circuit and a low-potential power supply (GND), monitors the voltage generated when the current flowing in the bridge circuit flows in the sense resistor, and thereby controls the switching on and off of the transistors in the bridge circuit. Accordingly, power is needlessly consumed by the sense resistor, which hampers reduction of power consumption. Also, since the sense resistor is provided as an external part of a circuit device (IC), the number of parts for the electronic apparatus in which the circuit device is incorporated increases, incurring problems such as an increase in cost.
According to some aspects of the invention, it is possible to provide a circuit device and an electronic apparatus in which reduction of power consumption, reduction of the number of parts, and the like can be realized by eliminating the need for a sense resistor.